Testing apparatus for multiple switchboards



(No Model.)

F. R. MoBER-TY.

TESTING APPARATUS FOR MULTIPLE SWITGHBOARDS. No. 509,932. Patented Dec.5,1893.

UNITED STATES PATENT DFFICE.

FRANK R. MOBERTY, OF DQWNERS GROVE, ASSIGNOR TO THE IVESTERN ELECTRICCOMPANY, OF CHICAGO, ILLINOIS.

TESTING APPARATUS FOR MULTIPLE SWITCHBOARDS.

SPECIFICATION forming part of Letters Patent No. 509,932, dated December5, 1893.

' Application filed February 7, 1893. Serial No. 461,413. (No model.)

To all whom it may concern.-

Be it known that I, FRANK R. MOBERTY, a citizen of the United States,residing at Downers Grove, in the county of Du Page and State ofIllinois, have invented a certain new and useful Improvement in TestingApparatus for Multiple Switchboards, (Case No. 5,) of which thefollowing is a full, clear, concise, and exact description, referencebeing had to the accompanying drawings, forming a" part of thisspecification.

My invention relates to testing apparatus for multiple switchboards oftelephone exchange central stations.

As is well known in the art, central stations of exchange systemscomprising a large number of telephone lines are provided withswitchboards whereby any line may be connected with anyother line. Theswitchboard is commonly divided into a number of sections upon each ofwhich are disposed the annunciators of acertain numberof subscribers,each group of annunciators being under the care of an attendantoperator; in order that any operator may make connection between any twolines at her own section of the multiple switchboard, spring-jacks orterminal sockets, one for each line connected with its particular line,are provided upon each section of the switchboard. It is necessary,however, that an operator at one section of the switchboard shall beable to determine whether or not any required telephone line is alreadyin use or connected at some other section of the switchboard. The devicewhereby an operator is thus enabled to determine whether any line is inuse or not is commonly known as the test system. Ordinarily, in multipleswitchboards for exchanges having metallic circuit lines, or comprisingboth metallic circuit and grounded lines, the test system consists of agrounded battery or other source of electric current connected with theloop plugs whereby connection is established with a line, and adapted tobe crossed with one of the contact pieces of the springjack into whichthe plug may be inserted, and a grounded testing plug adapted to beapplied to the corresponding contact piece of any springjack, thetesting plug including in its branch circuit a telephone or otherresponsive device. Thus when connection is made with any line, certaincontact pieces of all the springjacks of that line are electrified to adifference of potential from the earth, and whenever the grounded testplug is applied, in testing, to that contact piece, a current is createdthrough the telephone or other responsive device which indicates to theoperator making the test that the line tested is already in use. Mostcommonly, the responsive device employed is the operators telephonereceiver, the response being a click in the telephone. Telephone linesare, however, subject to external electrical influences which inducecurrents or static charges upon them; such currents or charges escapingto earth through the test circuit cause false clicks and signals in theresponsive device and give rise to confusion in the operation ofswitching.

It is the object of my invention to provide a test signal of a characterdistinct and different from any click or similar sound which might becaused by the discharge of a static charge upon the lines, the testsignal being at the sametime of onlymomentaryduration. Attempts haveheretofore been made to produce such individualized or characteristictest signals, usually as a musicaltone. It is desirable that the signalbe of veryshort duration in order that it may not be required that thedevice producingthe signal shall be disconnected so as to preventinterference with the.

operators telephonic apparatus. This has been accomplished heretofore bymechanical devices which have required comparatively strong currents fortheir operation, and have been slow and unreliable in their responses.

My invention consists of a condenser, a resistance, and a vibratingcircuit breaker or rheotome in the test circuit, and means foroccasionally or continuously discharging the condenser.

In the operation of testing, the condenser is charged by theintermittent testing current, the time of charging being madecomparatively long by the inclusion of the resistance in the testcircuit; whereby, during the flow of the charging current, a musicaltone is produced in the telephone in the circuit. The test signal isthus rendered characteristic and individualized, and at the same timelimited to short duration without the employment or intervention ofmechanical devices. In order to discharge the condenser after each testsignal, I preferably place a coil of high resistance and self-inductionin shunt about the condenser, through which the discharge of thecondenser continuously takes place. It will be understood that thecharging of thecondenser is not prevented by this coil, since thecondenser is charged to the difference of potential which is set upbetween the terminals of the high resistance shunt. The resistance coilis preferably arranged as a shunt about both the condenser and thevibrating circuit breaker, in order that continuous currents, escapingthrough the high resistance shunt, may not produce a sound in thetelephone.

I have sometimes employed a different device for discharging thecondenser, consisting of contact points adapted to be closed together bythe test plug when out of use, and when closed together, to shortcircuit the condenser; thus when the testing plug was raised to make atest, the condenser was put into condition to receive the charge.

I have illustrated my invention in the accompanying drawings, Figures 1and 2.

In Fig. 1 I have shown two substations, each connected by a metalliccircuit with an annunciator and springjack switches at a central office,the annunciators and springjacks being supposed to be located upondifferent switchboards, the usual connecting apparatus, and my improvedtesting apparatus having means for continuously discharging thecondenser. Fig. 2 represents the mechanism for use in connection withthe testing plug to discharge or short circuit the condenser while theplug is out of use.

Referring to Fig. 1 of the drawings, the substations 1 and 2 aresupposed to be equipped with the ordinary substation apparatus in commonuse in telephone exchange systems. The apparatusat substation 1 forexample is connected by lines a, a with springjacks b b at the centraloffice and also with an in dividual annunciator c thereat. Thespringjacks b and b are of ordinary construction, each having alinespring d and a test ring (1 connected with the different sides a and aof the line circuit, respectively, a normal resting contact 01 beingarranged for the spring (1 through which the line circuit extends to thenext jack. The resting contact (1 of the last springjack of the seriesis connected with one terminal of the annunciator a, so that the latteris disconnected whenever a plug is in serted into any springjack therebyraising the line spring of that jack from its normal resting contact.The springjacks b and b of lines 1 and 2 are supposed to be located uponone section e of multiple switchboard, and the springjacks b and b to belocated upon another section 6' of the switchboard, their respectiveannunciators c and 0 being located upon the different boards, in orderthat the annunciators may be under the care of different operators.

The appliances provided for the use of the operator in placing two linesin communication are also of the usual and well known character. Pairsof connecting plugs fand f are provided, each plug consisting of .twoparts insulated from each other, one being arranged to connect with theline spring 61 and the other with the test ring d of a springjack intowhich it may be inserted; the differout parts of the two plugs of a pairare connected by electrical conductors grandg'. In the conductors g gare included two ringing keys h and h, either of which is adapted, whendepressed, to disconnectone of the plugs from the other and to connectits different portions to the terminals vi and e" of a callinggenerator, not shown. The contact springs of a listening key areconnected with each cord circuit 9 g, the corresponding contact anvilsconstituting the terminals of the operators telephone set 1, whereby thetelephone set may be connected in abridge between the different. sidesof the circuit in order that the operator may communicate with thesubscribers with whose linesthe cord circuit is connected. Aclearing-out annunciator m is also included in a permanent bridgeconnection between the conductors g g to receive the signals fordisconnection upon the completion of conversation.

A ground connection is extended from the center of the coil of theoperators telephone receiver Z to earth in the usual manner. In myinvention I include in this ground branch a condenser and a device forrendering the current through it undulatory or intermittent, as avibrating circuit breaker or rheotome.

In the branch n from the telephone Z to earth is shown included acondenser n and the contact points 0 and 0 of a vibrating circuitbreaker W. The condenser n may be of one microfarad capacity, or more,as desired, the duration of the tone depending 'upon the capacity of thecondenser and the resistance of the circuit. To preventthe too rapidcharging of the condenser 11 I include a resistance a in the circuit;the resistance may be one thousand ohms, or more, if desired. Toaccomplish the discharge of the condenser n, a resistance coil n isplaced in shunt thereof; this coil 07. maybe of ten thousand ohmsresistance and may, with advantage, have considerable inductance toimpede the passage of telephonic or rapidly undulating currents throughit. 7

The different operations of signaling from the substation to the centralstation, and connecting lines, and testing to determine whether thelines are already in use or not, are all well known and are described innumerous patents; hence I will trace these operations only very briefly,and will pay especial attention to my improvement in the testingapparatus and to its operation. A subscriber, desiring to converse withanother subscriber of the exchange system, sendsa signal to the centralstation by rotating the armature of his generator, as usual, suppose,for example, that subscriber at station 2 desires connection withsubstation 1; the signaling current thus sent finds circuit over lines aa to the central oflice and through individual annunciator 'c thereat,operating the annunciator and indicating the signal to the attendant atswitchboard e. The operator at this switchboard then inserts one plug ofa pair into the springjack b of that line at her board, and depressesher listening key is, whereby her telephone set 1 is connected with theline circuit a a and she is enabled to receive the order from subscriberat station 2; she then tests the springjack 1) of line to station 1 ather board to determine whether that line is already in use or not at thesection e of the switchboard. I will not, at present, follow thisoperation of testing, but will revert to itiu connection with myimprovement alittle later. Assume, however, that she finds the line tostation 1 not in use; she then inserts the plug, with which she has madethe test, fully into the springjack of the line desired. The substations1 and 2 are shown thus connected by means of the cord circuit atswitchboard e. Having established connection with line to station 1, theoperator depresses her calling key h, therebylooping the callinggeneratorinto the line circuit in the usual manner to senda call signalto the substation. When the called subscriber has responded to thesignal and removed his telephone from its switch hook,

I the subscribers at the substations arein communication. Havingsatisfied herself that the connection has been properly made, theoperator allows the plunger of her listening key It to rise, thusdisconnecting her telephone set from the line circuit. When thesubscribers have completed their conversation, either of them mayoperate his calling generator, and the signaling current therefrom willfind circuit to the cord circuit 9 g and thence through the clearing-outannunciator, which will be operated and will indicate the signal fordisconnection to the attendant, who will proceed to remove theconnecting plugs from the springjacks of the lines, and will thusrestore the lines to their normal condition.

I will now describe the apparatus and the mode of testing at anyswitchboard to determine whether a line called for is already in use ornot at some other switchboard. The test rings or pieces d of thedifferent springjacks of each line are connected together throughout thecentral station, and are normally insulated from the earth. If anoperatorshould apply the tip of a testing plug to the test ring, as theplug f is shown applied to the test ring of springjack b at board e, hertele phone Z would be includedin abranch circuitfrom the test ringthrough one contact spring of the listening keyk to the telephone,through one half of the coil thereof, to earth branch n, thence throughthe condenser 01' and the resistance n in parallel, to the resistance97. and thence through the latter to earth. This circuit, however, doesnot contain any source of current, and hence no response is produced inthe telephone receiver Z when an idle line is tested. But when aconnecting plug is inserted into a springjack of the line, the sleeve ofthe plug, which is connected by way of the conductor g, retardation coil19, and battery q to earth, makes contact with the test ring of thespringjack and thus causes the entire series of test rings to beelectrified to a difference of potential from the earth. When, now, atest ring of this line is touched with a testing plug, as plug f, acurrent es-.

capes through the circuit before traced including the operatorstelephone Z. During the first momentof contact between the plug f andthe test ring, the current fiows directly into the condenser n, throughthevibrating contacts 0 0' and the resistance 91 to earth; anundulatorycurrent thus traverses the telephone Z and produces a musical tonetherein. In a moment, however, the condenser 71. becomes fully chargedand the current ceases to flow through the branch including thecondenser and the contacts 0 o, and the musical tone in the telephone ldisappears. A slight current may continue to flow through the resistancecoil n to earth,

but this current will be of continuous char acter and will produce nosound in the telephone l. There is thus produced in the telephone Z' amusical tone which is loudest at its inception and which rapidly fadesor decreases Io silence. The duration of the tone obviously depends uponthe length of time required by the condenser 71. to become fullycharged, and hence may be increased by increasing the capacity of thecondenser orthe resistance a I find a capacity of one microfarad to besufficient for the condenser n, and a resistance of from one thousand tofive thousand ohms to be sufficient for the coil u The moment the testplug f is withdrawn from contact with the test ring (1, the condenser nbegins to discharge through the resistance coil or, and the discharge isvery soon complete. The testing plug f may thus be quickly tapped uponthe test ring (1, or upon different test rings in quick succession, andat each application a musical tone, lasting a fraction of a second, isproduced in the telephone Z.

In Fig. 2 I have shown a different appliance for discharging condenser'n. In this figure a portion of one of the operators outfits is shown,comprising the two connecting plugsff, the conductors g g joining thedifferentcontact pieces of the plugs, the listening key it, theoperators telephone Z adapted to be connected with conductors g g bymeans resistance 72 in a ground branch from the center of the telephone.In this modification, a contact piece or plate r is provided upn whichthe testing plug f normally rests, and with which the sleeve thereofmakes electrical contact. This piece r is connected by a wire 3 with theground branch n in such a manner that when the apparatus is in theposition shown, wire 8 completes a shunt about the condenser 91,; thus,in the figure, the circuit may be traced from one side of condenser nthrough the rheotome contacts 0 0' to the wire 8, thence to the piece'1', the sleeve of plugf', to the conductor g and thence to thecorresponding contact spring of the key It, thence through one-half ofthe telephone Z to the other side of the condenser; hence, as long asthe testing plug f remains idle or not in use, and the key 70 is inposition to connect the telephone with that cord circuit, the condenseris permitted to discharge through the circuit thus formed; but when theoperator raises the plug f from its socket to make a test, the shortcircuit about the condenser n is automatically broken and the condenseris in condition to produce a momentary test signal in the manner beforedescribed.

It will be understood that a single condenser n' and rheotome n areprovided for each operator, since the testing apparatus is connectedonly with the pair of plugs which the operator may be using at anyparticular moment.

Having thus described my invention, I claim as new and desire to secureby Letters Patent- 1. The method of producing a tone of momentaryduration in a telephone without mechanically opening the circuit, whichconsists in charging a condenser in a circuit including the telephone bymeans of a direct current of an undulatory or pulsatory character,substantially as described.

2. The combination in a normally discontinuous test circuit including asource of electromotive force, of a condenser, a telephone, a deviceadapted to render the current through it pulsatory or alternating, andmeans for closing the said test circuit, whereby when said circuit isclosed a tone of short duration is produced in said telephone,substantially as described.

3. The combination in a normally discontinuous test circuit including asource of electromotive force, of a condenser, a telephone and a devicefor rendering current through it pulsatory or undulatory in characterincluded in said circuit, a shunt circuit about said condenser, andmeans for closing said test circuit, substantially as described.

4.- The combination with a test circuit for multiple switchboards,normally discontinuous at two points, of a source of electromotive forcein said circuit, a condenser, a telephone and a device for renderingcurrent through it of pulsatory or undulatory character, a shunt circuitof high resistance about said condenser, and means for closing saidcircuit at each of its points of normal discontinuity, substantially asdescribed.

In witness whereof I hereunto subscribe my name this 17th day ofNovember, A. D. 1892.

FRANK R. MGBERTY.

Witnesses:

ELLA EDLER, LUCILE RUSSELL.

